Fitbit, which makes fitness wearable devices including the Fitbit Surge smartwatch, saw its shares open for trading on Thursday at $30.40, good for a 52% gain, which valued the company at $6.2 billion. The valuation makes Fitbit one of the most valuable consumer technologies in the world.

Demand for the IPO was strong, with Fitbit raising $732 million, higher than initially expected. Fitbit sold some of its existing investors 36.6 million shares for $20 a share, up from its initial offering of 34.5 million shares of $17 to $19 a share. Fitbit initially said it expected to sell its shares between $14 and $16.

Shares of Fitbit closed the regular session at $29.68, good for a 48.4% gain over its $20 initial offering price, valuing the company at $6.08 billion. More than 50 million shares exchanged hands on its first day of trading.

At $20 a share, Fitbit was valued at $4.1 billion.

San Francisco-based Fitbit is one of the more financially sound technology companies to go public recently. In 2014, the company ended the year with $745.4 million in revenue, generating net income of $131.8 million with adjusted EBITDA of $191 million. That's a significant improvement over 2013, when it earned $79 million on $271.1 million in revenue.

TheStreet's Jim Cramer said Fitbit "is a bit of a gem. It is not expensive as high as $38-40 because that's where it sells roughly even with GoPro which is the other high growth company to compare it with," Cramer said. "The company is fast growing AND very profitable and you typically do not see that among the tech IPOs so it is a bit of a gem."

In the first three months of 2015, Fitbit said it generated $336.8 million in revenue, with net income of $48 million and adjusted EBITDA of $93.4 million.

Despite its fiscal strength, Fitbit has its share of worries, including the Apple (AAPL - Get Report) Watch, which recently went on sale in the company's stores after being sold exclusively online.

Fitbit listed Apple, among several other technology companies in its risks portion of its filing, noting, "For example, Apple has recently introduced the Apple Watch smartwatch, with broad-based functionalities, including some health and fitness tracking capabilities."

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